Preventive and persuasive actions against drunk driving

ABSTRACT

A vehicle safety system is provided that includes an alcohol concentration determining arrangement. A control unit is adapted to receive and analyze data from the alcohol concentration determining arrangement and output a blocking signal or a dissuasion signal under certain conditions. A blocking arrangement is adapted to prevent driving of the vehicle by the vehicle occupant upon receipt of a blocking signal. An output device is adapted to receive the dissuasion signal and to present a warning to the vehicle occupant to dissuade the occupant from driving the vehicle. The control unit is operable to categorize the concentration of alcohol in the occupant&#39;s blood into one of three categories: a low concentration category, in which the blocking signal will not be generated, a high concentration category, in which the blocking signal will be generated, and an intermediate category, in which the dissuasion signal will be generated.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to PCT patent applicationPCT/SE2007/050896 filed Nov. 23, 2007.

FIELD OF THE INVENTION

The present invention relates to methods and system designed to presenttraffic accidents due to drunk driving. More specifically, the inventionrelates to systems and methods employing breath analysis to detect thepresence and concentration of alcohol.

BACKGROUND OF THE INVENTION

In Anglo-American nomenclature, a device utilizing breath analysis todetect alcohol and acting on the results are normally referred to as analcohol interlock, or by the shorter term “alcolock.” The preventiveeffect of these devices have been demonstrated, along with severalpositive side effects, especially for the rehabilitation of driversalready convicted for drunk driving, and as a tool for quality assuranceof transportation services.

The typical purpose of an alcohol interlock is to prevent drunk driving.Technically, this is implemented by disabling the start of the engine,unless a breath sample with little or no alcohol concentration has beenprovided. A drunken person with affected driving capability andjudgement is thus physically prevented from driving, thereby eliminatingpossible damage to life and property caused by driving influenced byalcohol. The concentration limit used to determine whether the alcoholinterlock enables or disables the vehicle, also called “blocking” or“unblocking”, normally coincides with the legal limit of alcoholconsumption allowed for driving.

Regardless of their obvious merits, the idea of alcohol interlocks issomewhat controversial from the point of view of personal integrity andresponsibility. A vehicle owner may perceive the alcohol interlock asrestricting access to private property, and hence an infringement onpersonal integrity. In addition, a person accused of drunk driving mayclaim at least partial irresponsibility, if his or her vehicle wasequipped with an alcohol interlock and was still drivable. Both issuesof integrity and responsibility touch upon the possibility of falseblockings and unblockings.

Suppliers of alcohol interlocks are vague about the influence ofinevitable measurement errors, which cause false outputs at a ratedepending on the error magnitude. A highly precise instrument will giverise to few false outputs. If many drivers make use of this precision todrive slightly below the limit rather than refraining from driving, thenumber of intoxicated drivers may increase rather than decrease, thuspartly undermining the purpose of alcohol interlocks. On the other hand,a device with a large error will frequently block falsely. If routes tocircumvention are introduced to alleviate this problem, the main purposewill again be undermined.

Cost, inconvenience and time consumption are common additional argumentsagainst alcohol interlocks, especially from drivers who are moderateconsumers of alcohol. The possibility of circumvention or manipulation,for example, by asking someone else to provide the breath sample orbypassing the interlock, is another problem.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a vehicle safety system isprovided that includes an alcohol concentration determining arrangementfor making a determination as to the concentration of alcohol in theblood of a vehicle occupant. The system also includes a control unitadapted to receive and analyze data from the alcohol concentrationdetermining arrangement, and based upon the results of the analysis,output a blocking signal or a dissuasion signal. In some embodiments,the systems may further include a blocking arrangement adapted toreceive the blocking signal and to prevent driving of the vehicle by thevehicle occupant and an output device adapted to receive the dissuasionsignal and to present one or more warnings to the vehicle occupant todissuade the occupant from driving the vehicle. The control unit may beoperable to categorize the concentration of alcohol in the occupant'sblood into one of three categories. Three categories may include, forexample, a low concentration category, in which the blocking signal willnot be generated, a high concentration category, in which the blockingsignal will be generated, and an intermediate category, in which theblocking signal will not be generated and the dissuasion signal will begenerated.

In some forms, the alcohol concentration determination arrangement isconfigured to analyze a sample of the occupant's breath. The warningoutput by the output device may include auditory, visual and/or hapticstimulation. The output of the output device may include illumination ofa light source, the generation of a sound, the generation of a verbalmessage, the display of text, and/or vibratory stimulation of a part ofthe driver's body. In addition, the output of the output device may varydepending upon the concentration of alcohol in the occupant's blood.

In another aspect of the present invention, a method of controllingvehicle systems is provided. The method includes steps of determining aconcentration of alcohol in the blood of a vehicle occupant andcategorizing the concentration of alcohol in the occupant's blood intoat least one of three categories, including a low concentrationcategory, an intermediate category, and a high concentration category.If the determined concentration of alcohol in the blood of the occupantfalls into the high concentration category, the disclosed methodprevents the driving of the vehicle by the occupant. If the determinedconcentration of alcohol in the blood of the occupant falls into theintermediate category, the disclosed method includes allowing thevehicle occupant to drive the vehicle, and presenting one or morewarnings to the vehicle occupant to dissuade the occupant from drivingthe vehicle.

In some forms, if the concentration of alcohol in the occupant's bloodis determined to fall into the low category, the warnings are notpresented to the vehicle occupant. A computer program comprisingcomputer program code may be implemented to apply the steps of thedisclosed method. The computer program may be embodied on a computerreadable medium.

In another aspect of the present invention provides a method and systemfor the prevention and persuasion of driving a vehicle under theinfluence of alcohol is provided that includes the control ofdrivability of a vehicle into at least three categories. The categoriesinclude unrestricted unblocking, restricted unblocking, and blocking,respectively, based on the passing of system self-test, the approval ofbreath sample, and on the alcohol concentration of the breath samplebeing correspondingly categorized into low, moderate and high.

The system self-test may include means to differentiate between severalcategories of technical errors and attempts at circumvention ormanipulation, leading to different categories of drivability. Forexample, unprovoked technical error could be configured to lead to thecategory of restricted unblocking, whereas attempts at circumvention ormanipulation could be configured to lead to the category of blocking.

Furthermore, the category of restricted drivability could include meansfor persuasion or discomfort, for example, by auditory, visual and/orhaptic stimulation intended to provoke the attention of the driver withintensity and persuasiveness increasing with increasing alcoholconcentration. Based on the amount of elapsed time from the breathsample acceptance, for example, the means for persuasion or discomfortcould be exerted by a flashing source of light, a high-intensity tone ofsound at audible frequency or infrasound, verbal message urging theperson to stop the vehicle, communicated as display text or byartificial voice, vibratory means exerted at or within the driver'sseat, and/or the activation of a warning blinker intended to provoke theattention of other road-users.

In some variations, first and second distinct limit values of breathalcohol concentration may be defined to separate categories ofconcentration, because at the category of moderate concentration,significant reduction of capability to handle critical trafficsituations in a normal person is known to occur, and at the category ofhigh concentration, significant impairment of judgment is known tooccur. The first and second limit values may be defined to differ by atleast a factor of two, and to coincide with common legal concentrationlimits. For example, the first and second operational limits may be 0.1and 0.25 mg/l, respectively.

In some forms, the present invention provides a probability of falseblockings/unblockings that does not exceed 1%.

The breath sample approval may be determined by measurements performedat or in the close vicinity of the mouth of the person, indicating asource of air with alveolar composition with respect to carbon dioxideconcentration, humidity, temperature or any combination of theseentities, including timing relations. The breath sample approval may beinfluenced by signals indicating conditions of the vehicle, includingopening/closure of the main lock of the vehicle, opening/closure of doorto driver's seat, attachment/detachment of driver's seat belt, and/orposition of the ignition key.

In some variations, determination of the alcohol concentration may bebased on the measurement of infrared absorption within a wavelengthinterval known to possess absorption properties specific to alcohol.Drivability may be controlled by actuation onto the ignition key,solenoid, start motor, fuel injection unit, steering wheel, or gearcontrol of the vehicle.

The category of unprovoked errors may be localized to the internalhardware or software of the system, whereas said category of provokederrors may be localized to the boundaries of the system, with respect tothe vehicle system, the sensors, or the user interface.

In some forms of the present invention, the sensor unit may includesensor elements configured to respond to alcohol concentration, and anycombination of tracer signals of carbon dioxide concentration, humidityand temperature. A computational unit may be provided that includesmeans for the execution of pre-programmed arithmetic, logical andsequential operations. A memory unit may be provided for temporary orpermanent storage of information. A user communication unit may beprovided for the display or transfer of information relevant to thedriver and receiving input control signals from the driver. A vehicleinterface may be provided for signal transfer between the computationalunits. An actuator unit may be provided for the control of thedrivability categories.

The system may further include a housing adapted for single-handoperation by the driver. The housing may accommodate, for example, thesensor and user communication units, and a docking station for permanentpositioning of the housing between occasions of use. The docking stationmay include a power module and may be an integrated part of instrumentpanel of the vehicle. In some forms, the sensor and user communicationunits may be an integrated part of the steering wheel of the vehicle. Insome variations, a pocket-sized handheld unit may include the sensor andcommunication units, which may include wireless signal communication tothe vehicle. Wireless signal communication may occur within the parts ofthe system according to industrial standards, for example, Bluetooth,ZigBee, or RKE.

BRIEF DESCRIPTIONS OF THE DRAWINGS

In order that the present invention may be more readily understood,embodiments thereof will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a flow diagram illustrating the sequence of events for thedetermination of categories according to an embodiment of the presentinvention;

FIG. 2 is a graph of probabilities related to category attribution, inaccordance with the principles of the present invention; and

FIG. 3 is a schematic block diagram of the system architecture for usewith embodiments of the present invention.

DETAILED DESCRIPTIONS OF THE INVENTION

In accordance with embodiments of the present invention, a thirdcategory of drivability is introduced between the blocking andunblocking conditions. The third category includes restrictedunblocking, which includes a condition in which a moderately intoxicateddriver is persuasively informed about the reason for the restriction andurged to take an informed decision whether to interrupt the drivingoperation or not. The reason could be moderate alcohol intoxicationrevealed by the previous breath test, but could also be due to someunprovoked technical error.

The three categories of drivability of the present invention may belinked to corresponding categories of alcohol concentration within abreath sample provided by the driver: low, moderate and highconcentration. By high concentration is meant a level of intoxication atwhich a person's judgment is significantly affected. At the otherextreme, low concentration, neither a person's driving capacity norhis/her judgment are significantly reduced by intoxication. At moderateconcentrations, the driver's ability to handle critical trafficsituations is likely to be reduced, however, with remaining sense ofjudgment, including receptivity to persuasion.

The influence of alcohol on behavior and capabilities varies from oneperson to another, and may also vary from one occasion to another in anyindividual person. On the other hand, a device controlling drivabilityof a vehicle should preferably operate on the basis of clearly definedlimit values separating the three categories of breath alcoholconcentration. Preferably, the first and second limit values separatingthe three categories differ by a factor of two or more, and coincidewith established legal concentration limits.

In Sweden, vehicle driving is prohibited above a breath alcoholconcentration of 0.1 mg/l, which approximately corresponds to a bloodconcentration of 0.02%. In several European countries, the correspondinglegal limit in terms of breath alcohol concentration is 0.25 mg/l. Aninternational trend towards decreasing concentration limits can benoted. In the present invention, the preferred first concentration limitbetween low and moderate concentration is set at 0.1 mg/l, whereas thesecond concentration limit separating the moderate and highconcentrations is preferably set at 0.25 mg/l.

In the following text, blockings are defined as false when they occurfor a driver with zero alcohol concentration. Correspondingly, falseunblockings are defined as those occurring in a driver with alcoholconcentration at or above the concentration limit (CL), equaling thelimit between moderate and high alcohol concentration, that is thetransition between the unblocking and blocking conditions.

The probability of false blockings and unblockings is closely related tomeasurement errors, and to the location of the trigger level. If theerror distribution is symmetric, and false blockings and unblockings areequally undesirable, the trigger level should be located at half theconcentration limit, resulting in equal probabilities of false blockingsand unblockings. For a normal error distribution with standard deviationσ, the probability of blocking, PB as a function of the alcoholconcentration X normalized to CL can be determined by integrating theerror distribution function:

$\begin{matrix}{{{PB}(X)} = {\frac{1}{\sqrt{2\pi}}{\int_{- \infty}^{X/\sigma}{{\mathbb{e}}^{{(\frac{x - {{CL}/2}}{\sigma})}^{2}}\ {\mathbb{d}x}}}}} & (1)\end{matrix}$The probability of unblocking PU(X) is simply:PU(X)=1−PB(X)  (2)Evidently, the probabilities of blocking and unblocking depend on theratio between the concentration limit and the standard deviation, CL/σ.More specifically, the expression for the probability PF of falseblockings becomes:

$\begin{matrix}{{{PF}\left( {{CL}/\sigma} \right)} = {1 - {\frac{1}{\sqrt{2\pi}}{\int_{0}^{{CL}/\sigma}{{\mathbb{e}}^{{(\frac{x - {{CL}/2}}{\sigma})}^{2}}\ {\mathbb{d}x}}}}}} & (3)\end{matrix}$For symmetry reasons, this probability may also be expressed in a formwhich more easily lends itself to numerical calculations:

$\begin{matrix}{{{PF}\left( {{CL}/\sigma} \right)} = {2 \cdot \left\lbrack {1 - {\frac{1}{\sqrt{2\pi}}{\int_{- \infty}^{{CL}/\sigma}{{\mathbb{e}}^{{(\frac{x - {{CL}/2}}{\sigma})}^{2}}\ {\mathbb{d}x}}}}} \right\rbrack}} & (4)\end{matrix}$Inserting numerical values into eq. (4), probabilities may be calculatedfor different ratios CL/σ. Combining the requirements on measurementerror set by European industrial standard EN 50436-2 for alcoholinterlocks with the Swedish legal limit results in CL/σ=3.3, and a falseblocking/unblocking probability according to eq. (2) of 9.5*10⁻². In thepresent embodiment of the invention, the concentration limit is extendedby at least a factor of two, thus CL/σ=6.6. The corresponding falseblocking/unblocking probability is 9.7*10⁻⁴, representing a reduction ofapproximately two orders of magnitude.

The dramatically reduced probability of false blockings/unblockings inthis embodiment of the present invention will to a large extentneutralize the arguments against alcohol interlocks, including thoseconcerning personal integrity, responsibility and undermining ofpurpose.

The introduction of a third category of driveability is also put to usefor more intelligent handling of technical system errors and attempts atcircumvention. For a comparatively complex system such as that of analcohol interlock, the accumulated probability of technical systemerrors over the vehicle life cycle may become substantial.

In some embodiments of the present invention, a system self test isautomatically executed in conjunction with each breath test. In thesystem self test, provoked or unprovoked errors may be distinguishedfrom each other. Unprovoked errors may automatically set the vehicleinto the restricted unblocking condition, for example, whereas aprovoked error, attempts at circumvention, or manipulation may lead to ablocking condition. In both cases a specific error message may becommunicated to the driver. The system self test may, in principle,include all functional elements of the alcohol interlock, and may thusprovide adequate protection against circumvention, manipulation ormisuse. Preferably, it may be functionally integrated with the breathsampling process with no time delay.

Furthermore, embodiments of the present invention may involveintegration of system architecture. First, the functional devices maythemselves be highly integrated using combinations of semiconductortechnology developed for integrated circuits, MEMS (micro electromechanical systems) devices, PSoC (programmable system on chip). Second,structures, components and subsystems already available within thevehicle may be put to use for the system implementation. The integrativeapproach may result in significant cost savings with respect toproduction, use and maintenance.

The present invention seeks to provide an essential refinement of thepurpose, function and characteristics of alcohol interlocks. Whenimplemented at an industrial scale, embodiments of the invention areexpected to save human lives and property.

In the following, the term driver will be used to mean any person incontrol of a vehicle, irrespective of intention of, or actually,driving. The term road-user will be used to denote any passenger, orother person being potentially or actually influenced by the actions ofthe driver.

The flow diagram of FIG. 1 includes a starting condition 1 activated bya switch or other similar means. The switch may be coupled to thecentral lock of the vehicle, or the ignition key, but may alternativelybe completely independent of the vehicle system. Immediately upon start,a system test 2 is performed. Normally no errors are detected, since thesystem is designed for high reliability, using high quality componentsand assembly procedures. However, in this embodiment when a system erroris detected, it will either be categorized as an unprovoked error,outside the user's control, or as a possible result of some kind ofmanipulation. These cases will directly set the vehicle in restrictedunblocking and blocking conditions 6 or 7, respectively.

The categorization of errors into provoked or unprovoked is based onbasic criteria described in the table below.

TABLE Categorization of technical errors. Localization MechanismCategory External Circuits shorted or Provokable connections openedSensor “window” Blocking, bypass Provokable Internal hardware Componenterror Unprovokable Circuits shorted or opened Software Coding errorUnprovokable User interface Non-compliance with Provokable instructions

The possibility of provoking error, or manipulating the system, isbasically limited to the boundaries of the system with respect to theuser and the vehicle system, which may be either located at externalconnections, the “window” represented by the sensors, and/or the userinterface. Internal error sources related to either hardware orsoftware, and are not easily provoked, unless introduced by interventioninto design, programming, or maintenance routines normally inaccessibleto the user.

Since the categorization of errors is based on rules as outlined in thetable, it may be included in the system test. The detection of a systemerror will thus be shortly followed by its categorization into provokedor unprovoked, whereby a provoked error will result in blocking, andwhereas an unprovoked error will result in restricted drivability.

In this embodiment, after passing the system test 2 with no errors, thedriver is instructed to provide a breath sample 3 which will be analyzedwith respect to one or more of duration, volume, flow, pressure,temperature, humidity, carbon dioxide concentration, or othercharacteristic properties of an exhaled breath sample from a humanbeing. If a breath sample is not accepted, the driver will be instructedto make a new attempt. Repeated failures to deliver breath samples willbe interpreted as attempts at manipulation, which will set the vehiclein the blocking condition 7. This is accomplished by counting the numberof attempts, indicated as N and box 8 in FIG. 1. If accepted, the breathsample will be further analysed with respect to its alcoholconcentration 4.

Breath sampling is preferably performed in the vicinity of the driver'smouth after instruction to perform a forced and extensive exhalation inorder to ensure that deep lung air is included. A mouthpiece is notnecessarily used for sampling, since the dilution of a breath sampleobtained in free air may be determined by the simultaneous measurementof tracer signals, preferably carbon dioxide, humidity or temperature.Notably, the composition of alveolar air with respect to these entitiesis remarkably well-defined and stable. Furthermore, they possessspecific timing properties resulting from the presence of dead spacecorresponding to the upper airways. At normal ambient conditions,temperature and humidity increase more rapidly than carbon dioxide atthe onset of exhalation.

The analysis of alcohol concentration may be performed by means ofsensing and computational elements. A preferred method is infraredtransmission spectroscopy, in which a beam of infrared light istransmitted from a broadband source to a detector equipped withdispersive element enabling spectral analysis of the transmitted beam.The presence of alcohol within the transmission path provides a specificsignature of the detected signal, allowing both substance identificationand quantification. The signature is based on molecular properties ofalcohol resulting in specific infrared absorption characteristics.Alternatively, alcohol concentration may be measured by electrochemicalor semiconductor sensors, however, with lower specificity andreliability. Any other suitable arrangement for determining theconcentration of alcohol in the occupant's blood may also oralternatively be used.

The alcohol concentration is categorised as low, moderate or high,depending on pre-programmed criteria. Low concentration will lead to theunrestricted unblocking condition 5, moderate concentration to therestricted unblocking category 6, and high to the blocking condition 7.

The category of restricted unblocking 6 will include means of persuasionor discomfort, by auditory, visual and/or haptic stimulation intended toprovoke the attention of said driver. Preferably, the intensity andpersuasiveness of these means will increase with increasing alcoholconcentration, and elapsed time from the breath sample acceptance. Thestimulation is, for example, exerted by a flashing source of light, ahigh-intensity tone of sound at an audible frequency or as infrasound, averbal message urging a person to stop the vehicle, communicated asdisplay text or by artificial voice, vibratory means exerted at orwithin the driver's seat, and the activation of a warning blinkerintended to provoke the attention of other road-users.

In order to ensure that the breath sample is actually originating fromthe driver and not any other person, its acceptance is preferablyinfluenced by signals indicating conditions of the vehicle, includingopening/closure of main lock to the vehicle, opening/closure of the doorto driver's seat, attachment/detachment of the driver's seat belt, andposition of the ignition key. In modern vehicles, these signals arenormally already present.

FIG. 2 is a graph showing the unblocking/blocking probabilities as afunction of alcohol concentration normalized to CL. Curves for CL/σequaling 3.3 and 6.6 are included in the figure. As already inferred,CL/σ=3.3 corresponds to realistic performance and limit values. In thepresent invention, the corresponding CL/σ will at least double to 6.6.The graphs shown in FIG. 2 were obtained from numerical calculation ofEq. (2). For CL/σ=3.3 and zero concentration, the blocking probabilityis approximately equal to 0.05, which is equal to the probability ofunblocking at concentration=CL. These two probabilities add up to thetotal probability of false blockings/unblockings as already quotedabove. From FIG. 2, a dramatic reduction in the probability of falseblockings/unblockings when increasing CL/σ from 3.3 to 6.6 is evident.

FIG. 3 schematically depicts the architecture of a system embodying theinvention. Preferably, the system is comprised of two physicallydistinguishable block units: the driver interface unit 11, the vehicleinterface unit 12, with electronic communication with the main vehiclesystem 13.

The driver interface unit 11 includes a sensor unit 14 with sensorelements responding to alcohol concentration, and any combination ofcarbon dioxide concentration, humidity and temperature of the breathsample. Preferably, alcohol, carbon dioxide and water vapor (humidity)concentration is measured in a single cavity traversed with infraredradiation from a broadband blackbody source radiator. Different bandpassinterference or diffraction filters tuned to absorption bands specificto alcohol, carbon dioxide and water vapour, are being used in amultiple band infrared detector. The signal outputs from the detectorrepresents concentration of each of these entities. Temperature may bemeasured using thermocouples or resistive temperature sensor(s).

Typically, the signals from the sensor unit 14 are analog voltages whichrequire conversion into digital format in an analog to digital converter15, before they are transferred to the computational unit 16. This unitincludes means for the execution of pre-programmed arithmetic, logicaland sequential operations, memory unit for temporary or permanentstorage of information. The computational unit 16 is thus capable ofexecuting the operations outlined in FIG. 1, provided that eachoperational step has been adequately defined, compiled and stored in theprogram memory.

Also included in the driver interface unit 11 in this embodiment is anoutput device in the form of a user communication unit 17 for thedisplay or transfer of information relevant to the driver and receivinginput control signals from the driver. The communication unit may alsoinclude means for audible or haptic signal communication.

The driver interface 11 accommodating sensor and user communicationunits 14 and 17 are preferably packaged in a housing adapted forsingle-hand operation by the driver. In a preferred embodiment, thesensor and user communication units 14 and 17 constitute integratedparts of the steering wheel of the vehicle. Signal and power lines arepreferably in communication along the steering shaft. Alternatively,signals are communicated by wireless link, preferably using commonlyaccessed radio frequencies and protocols according to industrialstandards, such as Bluetooth or ZigBee.

In this embodiment, the driver and vehicle interfaces 11 and 12electronically communicate by means of interface circuitry 18, 19 via acommunication channel 20. Preferably, the communication is performed ina serial digital format, and encoded in order to prevent manipulation.Basically, the vehicle interface unit 12 relays the communicationbetween the driver interface 11 unit and the vehicle system 13 for thecontrol of the drivability categories, and performs a supervisory systemfunction in relation to the system self test described above. In orderto execute this supervisory function, the vehicle interface is equippedwith a computational unit 21, sensor and actuator units 23, 24, and adisplay unit 22.

In this embodiment, the vehicle interface 12 communicates with thevehicle system 13 by means of a communication channel 27, and interfacecircuitry 25, 26. Preferably, the communication channel 27 conforms tostandards for vehicle signal communication, for example, by the CAN busarrangement. Alternatively, signals are communicated by wireless link,preferably using commonly accessed radio frequencies and protocolsaccording to industrial standards, such as Bluetooth or ZigBee.

The system according to the invention is preferably directly orindirectly powered from the main vehicle power supply 28. The directpowering makes use of permanent power lines to each active unit asillustrated in FIG. 3. Indirect powering may involve one or morerechargeable batteries built into one or several units, for example, inthe driver interface 11.

Preferably, blocking of the driveability of the vehicle according to thecategory described above is controlled by actuation onto the ignitionkey, solenoid, start motor, fuel injection unit, steering wheel, or gearcontrol. In order to make manipulation more difficult, actuation of morethan one of these functions may be performed simultaneously, butdifferently at different occasions. The control of which functions areactuated at any one occasion is preferably stored in the program memoryof the computational units 16 or 21.

The restricted unblocking category of drivability may be implemented bya number of persuasive signals directed to the driver. These signals maybe activated via the user communication unit 17, or elements included inthe vehicle unit 13, for example, the warning blinker.

The physical implementation of the system according to the invention maytake several alternative forms. In a preferred embodiment, the driverinterface unit is embedded into a housing adapted for single-handoperation by the driver. The housing is accommodating the sensor,computational and user communication units 14, 16, and 18. The housingis adapted to a docking station for permanent positioning betweenoccasions of use. The docking station includes a power module and is anintegrated part of the instrument panel of the vehicle. The dockingstation includes the vehicle interface unit 12.

In another preferred embodiment, the driver interface unit 11 isembedded within a pocket-sized handheld unit including sensor,computational and communication units 14, 16, 18. According to thisembodiment, the pocket-sized unit communicates with the vehicleinterface 12 via a wireless link, preferably using standard frequenciesand protocols according to the industrial standards for remote keylessentry (RKE). In this case, simplex rather than duplex communication canbe used, reducing cost and improving user friendliness.

When used in this specification and claims, the terms “comprises” and“comprising” and variations thereof mean that the specified features,steps or integers are included. The terms are not to be interpreted toexclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilized forrealizing the invention in diverse forms thereof.

1. A vehicle safety system, comprising: an alcohol concentrationdetermining arrangement, for making a determination as to theconcentration of alcohol in the blood of a vehicle occupant; a controlunit adapted to receive and analyze data from the alcohol concentrationdetermining arrangement to create an analysis, and in dependence uponthe results of the analysis, the control unit being operable to outputone of a blocking signal and a warning signal; a blocking arrangement,adapted to receive the blocking signal and to prevent driving of thevehicle by the vehicle occupant; and an output device adapted to receivethe warning signal and to present at least one warning to the vehicleoccupant; wherein: the control unit is operable to categorize theconcentration of alcohol in the occupant's blood into one of threecategories, the categories including a low concentration category, inwhich the blocking signal will not be generated, a high concentrationcategory, in which the blocking signal will be generated, and anintermediate category, in which the blocking signal will not begenerated and the warning signal will be generated; the control systembeing configured to automatically execute a system self-test inconjunction with each breath test, to distinguish provoked andunprovoked errors from each other; to categorize an unprovoked error inthe intermediate category, and to categorize a provoked error in thehigh concentration category.
 2. The system according to claim 1, whereinthe alcohol concentration determination arrangement is operable toanalyze a sample of the occupant's breath.
 3. The system according toclaim 1, wherein the warning presented by the output device comprises atleast one of auditory, visual and haptic stimulation.
 4. The systemaccording to claim 3, wherein the warning of the output device comprisesat least one of the following: illumination of a light source,generation of a sound, generation of a verbal message, display of text,and vibratory stimulation of a part of the driver's body.
 5. The systemaccording to claim 3, wherein the warning of the output device variesdepending upon the concentration of alcohol in the occupant's blood. 6.A method of controlling vehicle systems, comprising: determining aconcentration of alcohol in the blood of a vehicle occupant to identifya determined concentration; categorizing the concentration of alcohol inthe occupant's blood into one of three categories, the categoriesincluding a low concentration category, an intermediate category, and ahigh concentration category; preventing the driving of the vehicle bythe occupant if the determined concentration of alcohol in the blood ofthe occupant is categorized in the high concentration category; andallowing the vehicle occupant to drive the vehicle and presenting atleast one warning to the vehicle occupant if the determinedconcentration of alcohol in the blood of the occupant is categorized inthe intermediate category; automatically executing a system self-test,distinguishing provoked and unprovoked errors from each other;categorizing an unprovoked error in the intermediate category, andcategorizing a provoked error in the high concentration category.
 7. Themethod according to claim 6 wherein, if the determined concentration ofalcohol in the occupant's blood is categorized in the low category, awarning is not presented to the vehicle occupant.
 8. A computer programembodied on a non-transitory computer-readable medium comprisingcomputer program code configured to perform the following steps when thecode is run on a computer: determining a concentration of alcohol in theblood of a vehicle occupant to identify a determined concentration;categorizing the concentration of alcohol in the occupant's blood intoone of three categories, the categories including a low concentrationcategory, an intermediate category, and a high concentration category;preventing the driving of the vehicle by the occupant if the determinedconcentration of alcohol in the blood of the occupant is categorized inthe high concentration category; allowing the vehicle occupant to drivethe vehicle and presenting at least one warning to the vehicle occupantif the determined concentration of alcohol in the blood of the occupantis categorized in the intermediate category; and not presenting awarning if the determined concentration of alcohol in the occupant'sblood is categorized in the low category; automatically executing asystem self-test, distinguishing provoked and unprovoked errors fromeach other; categorizing an unprovoked error in the intermediatecategory, and categorizing a provoked error in the high concentrationcategory.